Under the deal, reached last March, Turkey agreed to take back refugees, who had landed on the shores of Greek islands after illegally crossing the Aegean Sea from Turkey. For every Syrian returned to Turkey, a Syrian living in one of the refugee camps would be resettled in the EU. European leaders also pledged funds for Syrian refugees in Turkey and promised to grant its citizens visa-free travel in the Schengen area in exchange for Ankara's cooperation.

However, the agreement that became the pillar of the EU’s migration strategy was thrown into doubt because of a massive government crackdown on alleged supporters of the July 15 failed coup attempt, purging thousands in the military, police, the courts, schools, academia and the media.

The G20 summit, a gathering of leaders of world's richest countries, will take place on September 4-5 in the city of Hangzhou.